The invention relates to a method for warming up an internal combustion engine, especially of a motor vehicle, wherein fuel is injected into an intake manifold or into a combustion chamber and wherein a warm-up factor for increasing the injected fuel quantity is determined below an operating temperature of the engine. The invention likewise relates to a corresponding internal combustion engine as well as to a corresponding control apparatus for such an engine.
A method, internal combustion engine and a control apparatus of this kind are all known, for example, from a so-called intake manifold injection. There, fuel is injected into the intake manifold of the engine in homogeneous operation during the intake phase in order to then be inducted into the combustion chamber of the engine. Correspondingly, in a so-called direct-injection internal combustion engine, the fuel is injected into the combustion chamber directly during the induction phase or during the compression phase and is there combusted.
When warming up, in an engine, which is not operationally warm, an increased fuel quantity must be injected into the intake manifold or into the combustion chamber. This is carried out in a manner known per se with the aid of a warm-up factor which influences the quantity of fuel to be injected below the operating temperature of the engine.
The known determination of the warm-up factor is based on intake manifold injections and is therefore not flexibly useable. The known determination of the warm-up factor can only be used to a limited extent for direct-injection internal combustion engines.
The task of the invention is to provide a method for warming up an internal combustion engine with which a greater flexibility and especially a simplified application can be achieved for a simultaneously improved warm-up characteristic of the engine.
This task is solved in accordance with the invention in a method of the kind mentioned initially herein in that the warm-up factor is determined from a base factor and a load-dependent factor. The task is correspondingly solved in accordance with the invention in an internal combustion engine and in a control apparatus of the type mentioned initially herein.
With the separation of the base factor and the load-dependent factor in accordance with the invention, the last-mentioned factor can be determined for different modes of operation independently of the base factor. In this way, a simple use of the determination of the warm-up factor in accordance with the invention is possible for direct-injecting internal combustion engines.
Likewise, the base factor and the load-dependent factor can be applied independently of each other in accordance with the invention. The same applies also for the determination of the load-dependent factor in the different modes of operation of a direct-injecting internal combustion engine.
In the invention, it is especially not necessary to subsequently change the determination of the base factor in dependence upon a load being applied to the engine.
With the flexibility achieved in accordance with the invention, the invention is easily applicable to intake manifold injections. Here, the mutually independent application of the base factor and of the load-dependent factor is advantageously noted.
In advantageous embodiments of the invention, the load-dependent factor is determined in dependence upon an integrated air mass and/or an integrated fuel mass and/or a temperature of the engine and/or the load-dependent factor is determined in dependence upon a relative air charge and/or a relative fuel quantity and/or an actual or desired lambda and/or an actual or desired torque of the engine.
What is essential is that the load-dependent factor responds rapidly and flexibly to the load changes of the engine and/or to other changes of operating variables of the engine. From this results the advantage of a subjective good drivability of the engine even at low operating temperatures.
In a further advantageous embodiment of the invention, the base factor is determined in dependence upon the engine temperature. This defines an especially simple yet adequate possibility for determining the base factor.
In an advantageous configuration of the invention, the load-dependent factor and the base factor are additively logically coupled to each other. In this way, the factors, which are determined independently from each other in accordance with the invention, are again combined into the warm-up factor.
In an advantageous configuration of the invention, the load-dependent factor or the sum of the load-dependent factor and the base factor are weighted in dependence upon the rpm of the engine. The weighting therefore operates either on the load-dependent factor alone or on the sum of the load-dependent factor and the base factor. In this way, it is possible to carry out adaptations corresponding to the type of engine and with a view to the rpm weighting.
Of special significance is the realization of the method of the invention in the form of a control element which is provided for a control apparatus of an engine, especially of a motor vehicle. A program is stored on the control element which is capable of being run on a computer, especially on a microprocessor, and is suitable for executing the method according to the invention. In this case, the invention is realized by a program stored on the control element so that this control element, which is provided with the program, defines the invention in the same way as the method which the program can carry out. Especially an electric storage medium can be used as a control element, for example, a read-only-memory or a flash memory.
Further features, application possibilities and advantages of the invention will become apparent from the following description of embodiments of the invention which are illustrated in the drawing. All described or illustrated features define the subject matter of the invention by themselves or in any desired combination independently of their summary in the patent claims or their dependency as well as independently of their formulation or presentation in the description and/or in the drawing.